Enhancement: Updated all dependencies (Jetty8 - 9, Servlet 2.5 - 3.1)

Updated dependencies:

Server:
- Guava (16 -> 17)
- jetty (8 -> 9)
- servlet (2.5 -> 3.1)
- spring mvc (3.2.8 -> 4.0.6)
- spring-data (1.5.1 -> 1.6.1)
- spring-security (3.2.3 - 3.2.4)
- spring-amqp (1.3.1 -> 1.3.5)
- rabbitmq (3.2.4 -> 3.3.4)
- hibernate (4.3.4 -> 4.3.6)
- querydsl (3.3.2 -> 3.4.1)
- ehcache (2.8.1 -> 2.8.3)
- jackson (2.3.2 -> 2.4.1.1)
- apache-common-math (3.2 -> 3.3)
- supercsv (2.1.0 -> 2.2.0)

On the server org.eclipse.jetty:jetty-proxy was added and web.xml was adapted.

Client:
- GWT (2.6.0 -> 2.6.1)
- maven-gwt-plugin (2.5.0 -> 2.6.1)
- gwt-query (1.4.1 -> 1.4.2)
Removed maven.jetty.plugin.version. Only using jetty.version
Merge branch 'dependency_update'